This invention relates to a fluidic flowmeter, and more particularly to a fluidic flowmeter comprising a fluidic element including a converging passage, a jet nozzle disposed downstream of the converging passage, a diverging passage disposed downstream of the jet nozzle, a pair of control nozzles disposed between the jet nozzle and the diverging passage and opposed to each other across and in a direction substantially perpendicular to a direction in which a fluid jet shoots from the jet nozzle, and return passages connecting a downstream position of the diverging passage to the control nozzles, respectively.
This type of flowmeter utilizes Coanda effect, namely a phenomenon in which a fluid jet shooting from the jet nozzle stabilizes in a flow along one of inclined walls of the diverging passage, and a phenomenon in which the fluid jet shooting from the jet nozzle flows alternately along the two walls of the diverging passage by actions of fluid jet shooting alternately from the two control nozzles. This flowmeter measures flow rates on the basis of frequency variations resulting from the alternation of directions in which the fluid jet shooting from the jet nozzle flows.
Conventional fluidic flowmeters of the type described above comprise only one fluidic element including a jet nozzle which defines only one outlet opening. Where the outlet opening has a small area for the purpose of high sensitivity so that a small flow rate may be measured with high precision, a great pressure loss occurs rendering a desired measurement impossible at times of large flow rate. Conversely, where the outlet opening has a large area to permit a large flow rate to be measured with high precision, the measurement sensitivity becomes poor at times of small flow rate. Thus, the conventional fluidic flowmeters have room for improvement from the point of view of measuring range where great flow rate variations are involved.